Researchers say the spike in sex is due to extra time off, boozy parties (oops!) and New Year's resolutions to have children. Not surprisingly, all those holiday hook-ups translate into a slew of births in September, finds David Lam of the University of Michigan's Population Studies Center in Ann Arbor.

Many of my friends say that the holidays are when exes suddenly pop back into their lives. They chalk up rekindled romances to nostalgia; I call it the best present you could give--or get!